Philip alexander mackay



UNITED STATES PATENT OFFICE.

' PHILIP ALEXANDER MACKAY, on NEW YORK, iv. Y.

1,387,443. 7 V 7 No Drawing. Application filed April 4,

To all whom it may concern Be it known that I, PHILIP ALEXANDER MAoKAY,a citizen of the United States, re-

siding at New York city, county of New York, borough ofManhattan, Stateof New York, have invented certain new and use- .ful Methods ofObtaining Iron and Tin fro'm Tin Scrap, of which the following is becomewaste, material; is usually treatedbv' electrolytic recovery processes,caustic soda processes, or the well known chlorin recovery process, toseparate the tin from the iron, for the dual purpose of recovering tinand clean iron; scrap. V

The object of the present invention is to provide a simple method ofseparating the tin and iron to be found in tin scrap, so as to obtain abright iron. I

The invention consists inseparating the tin and iron in tin scrap .bvsubiccting the scrap to the action of sulfuric acid contain. ing sulfurtrioxid in solution e. oleum) until the tin is dissolved.

I have found that if the waste material is well cleaned and dried '(forwhich opera- 'tions processes are already Well known) and isdipped intosulfuric acid containingfree SO, in solution. 2'. 6., a solutio'n'knownunder the name of oleum; and the solution is sli htly Warm, that the tinis dissolved ouickly and the iron recovered not onlv free "from tin.butwhich remains after drying, in a bright condition; thus in contrast tosome other arocesses in which oxidation -takes place very quickly aftertreatment, thus lowering the commercial value of the ,iron. In statingthat the solution of oleuni is warm I do not imply that the bathmust beartificiallvheated before use. but'that the operations should beinitiated in a place hilVlIlQ a warm temperature as hereinaftedescribed.

The present invention may be carried into effect either as a contlnuousmethod, or a batch or intermittent system of treatment may be employed,and the following example shows the application of the batch, orintermittent svs em. in which apparatus of the type well known in thetinpickling in- Speci ficati on of Letters Patent.

METHOD or OBTAINING monlaivn TIN FROM TIN sonar.

1921. Serial No. 458,468.

dustrymay be employed. A batch of tin scrap is suspended in the oleumsolution 1n a. perforated vessel formed of material not attacked by theoleum in the concentrated or diluted condition, and ismechanicallyqnoved up and down in the oleum for a period of ten minutes,the oleum solution. being; at room temperature, or about 20 de greesCentigrade. The tin is readily removed inthe period of ten minutes. whenthe iron scrap is lifted from the oleumsolution andplunsred into a leadlined vessel. r o r inine water.

I also propose. as an alternative mean; of mani ulating? the batches ofscrap (i. c. movincr them within the-liquid). to utilize masrnets. i

A large proportion of the oxidized tin is carried into the second orwash vessel.

where. on dilution with the water. approrisulfid. or prefera'blv theexcess acid is re moved hv addinw iron to the so ution in make ferroussulfate. and the tin is precipi- Patented Aug. 9, 1921.

tated before all the acid is neutralized by the iron.

The tin left in solution in the o eum after a succession of batches havebeen treated. ,existspartlv in solution. ands portion senaratcs o insuspension in the oleum as SnOSnSO. and gradually settles to thebottomof the detinning' vessel: this mav be removed bv a cook or valvefrcm time to time and treated for the recovery of the-tin.

Successive batches of tin scrap are treated in the manner abovedescribed. and as th reactions proceed the tin is removed andthe'treated batches removed to the wate bath; the recovered scrap ironcarries with it by capillary attractiona weight of oleum varying from 4per cent. to 8 per cent. depending on the game of the scrap treated.

As someof thisoleum (usually an amount varving from '4 per centl to .8per cent. of the weight of scrap) is removed from the clown vat witheach batch of scrap removed therefrom, the level is made up "bv additionof fresh. oleum. and I'find in practice that I can maintain the oleum atav strength of so-called 10 per cent. oleum. this containing 10 percent. free SO which strength may be readily maintained by making up thisloss by addition of oleum of 20 per cent. strength.

At the same time I maintain equilibrium 2 menses of temperature of thebath within narrow limits, say, between degrees and 55 de greescentigrade.

During the period of ten minutes treatment of the first batch of scraptin by the oleum the temperature of the oleum solution rises sli 'htlyfrom the exothermic reaction of the oleuln acting upon the tin. As eachsucceeding batch is treated the temperature continues to rise until itreaches approximately degrees centigrade, and as the temperature rises,the time necessary for the removal of the tin is shortened until at thetemperature of 50 degrees centigrade it is possible to remove the tin inthree minutes on grades of scrap containing about 2 per cent. of tin.Should the temperature rise beyond (3., the bath may be cooled by a coldwater coil or jacket, This, however, is not usually necessary the lossof heat'by radiation and conduction being sufficient to prevent rise oftemperature above the stated degree. Hence the temperature control maybe regarded as more or less automatic. The following chemical reactionis involved as the base reaction:

It is to be noted. that no extraneous heating of the oleum solution isnecessary as the required temperatures above the temperature of theprocess chamber are wholly obtained by the exothermic reaction whichoccurs.

Although I have mentioned in this specilication that the iron scrap ispreviously cleaned and dried, this is not an essential.

to the process, but merely as an economy to save oleum and also tomaintain the detin ning vessel as clean as possible.

What I claim as new and useful, and of my own invention, and desire tosecure by Letters Patent, is :--v

short periods, and subsequently washing the residual -iron in water.

3. A method of separating the tin and iron in tin scrap in which thescrap is subjected' to the action of sulfuric acid containing freesulfur trioxid in solution, until the tin is dissolved, and maintaininga substantially constant temperature of the acid bath during thetreatment of successive quantities of scrap. 7

l. In the process of claim 2, the step of maintaining the temperature ofthe bath of sulfur trioxid in sulfuric acid about constant at between 45(1, and 55 C, and maintaining said solution at about a uniformconcentration throughout the opera tion.

5. In the method of separating the tin andv iron in tinscrap in whichthe scrap is sub jected to the action of sulfuric acid contain ing freesulfur trioxid in solution, until the tin is dissolved, the improvementwhich comprises conducting such operation at a temperature aboveordinary room temper ture, such temperature being wholly obtained andmaintained by exothermic chemical reaction.

6. In the method of separating the tin and iron in tin scrap in whichthe scrap is subjected to the action of sulfuric arid containing freesulfur trioxid in solution, until the tin is dissolved, the improvementwhich comprises conducting such operatirm at a temperature aboveordinary room temperature, such temperature being Wholly ob tained andmaintained by exothermic chemical reaction, and maintaining a constantconcentration of acid throughout the operation.

7. A method of separating the tin and iron in tin scrap in which thescrap is subjected. to the action of sulfuric acid, containingfreesulfur trioxid in solution by successively dipping the scrap in the acidfor short periods and subsequently washing the separated iron in water,the said treatment being conducted at a temperature of between about 45(3., and 55 during the treat ment of successive quantities of scrap, andmaintaining a constant concentration of the said acid during thetreatment of successive batches of such tin scrap therein.

8. A'IHQlShOCl of separating the tin and 'iron in tin scrap whichcomprises subjecting the scrap to the action of sulfuric acid'containingfree sulfur trioxid in solution by successively dipping the scrap in theacid. for short periods, and subsequently washing the separated iron inwater, and recovering the oxidized tin from the acid solution and thewater as set forth.

In testimon whereof I affix in si nature.

PHILIP ALEXANDER I /iA QKA Y.

